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A Black Hole Mystery Wrapped in a Firewall Paradox


by Dennis Overbye
The New York Times, August 12, 2013

This time, they say, Einstein might really be wrong.

A high-octane debate has broken out 
among the world’s physicists 
about what would happen 
if you jumped into a black hole, 
a fearsome gravitational monster 
that can swallow matter, energy and even light. 

You would die, of course, but how? 

Crushed smaller than a dust mote 
by monstrous gravity, 
as astronomers and science fiction writers 
have been telling us for decades? 

Or flash-fried by a firewall of energy, 
as an alarming new calculation seems to indicate?

This dire-sounding debate 
has spawned a profusion of papers, 
blog posts and workshops over the last year. 

At stake is not Einstein’s reputation, 
which is after all secure, 
or even the efficacy of our iPhones, 
but perhaps the basis 
of his general theory of relativity, 
the theory of gravity, 
on which our understanding 
of the universe is based. 

Or some other fundamental 
long-established principle of nature 
might have to be abandoned, 
but physicists don’t agree on which one, 
and they have been flip-flopping 
and changing positions almost weekly, 
with no resolution in sight.

“I was a yo-yo on this,” 
said one of the more prolific authors in the field, 
Leonard Susskind of Stanford. 

He paused and added, 
“I haven’t changed my mind 
in a few months now.”

Raphael Bousso, 
a theorist at the University of California, Berkeley,
said, “I’ve never been so surprised. 
I don’t know what to expect.”

You might wonder who cares, 
especially if encountering 
a black hole is not on your calendar. 

But some of the basic tenets 
of modern science 
and of Einstein’s theory 
are at stake in the “firewall paradox,” 
as it is known.

“It points to something missing 
in our understanding of gravity,” 
said Joseph Polchinski, 
of the Kavli Institute 
for Theoretical Physics 
in Santa Barbara, California, 
one of the theorists 
who set off this confusion. 

Down this rabbit hole are many 
of the jazzy magical mysteries 
of modern physics: Black holes. 

The shortcuts through space and time called wormholes. 

Quantum entanglement, 
also known as spooky action at a distance, 
in which particles separated by light-years 
can still instantaneously appear to remain connected. 

The reward for going down this hole 
could be a new understanding 
of why we think we live in a universe 
with space and time at all, 
with suitably unpredictable consequences. 

After all, if Einstein hadn’t been troubled 
a century ago by logical inconsistencies 
in the Newtonian universe, 
we might not have GPS systems, 
which rely on his theory of general relativity 
to keep time, in our pockets today.

Falling Bodies

Black holes are the most 
extreme predictions of Einstein’s theory, 
which describes how matter and energy 
warp the geometry of space and time 
the way a heavy sleeper causes a mattress to sag. 

Too much matter and energy in one place 
could cause space to sag so far 
that the matter inside it would disappear 
as if behind a magician’s cloak, 
collapsing endlessly to a point 
of infinite density known as a singularity. 

Einstein thought that idea was ridiculous 
when it was pointed out to him at the time, 
in 1916, but today astronomers agree 
that the universe is speckled 
with such dark monsters, 
including beasts lurking 
in the hearts of most galaxies 
that are millions and billions of time 
more massive than the Sun. 

Many of them resulted 
from the collapse of dead stars.

General relativity is based 
on what Einstein later called 
his “happiest thought,” 
that a freely falling person 
would not feel his weight. 

It is known simply 
as the equivalence principle; 
it says that empty space 
looks the same everywhere 
and to everyone.

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